Xuelder

Indie Game/Narrative Designer

Tech Warlock

Weird dude who makes weird things.

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stu
@stu

apparently companies are substituting 5% acidity vinegar with 4% acidity in the gallon jugs you buy when you're canning. nice subtle move from some MBA except that people's canned food won't be shelf stable


sirocyl
@sirocyl

Currently, the FDA mandate (File, PDF) is that 4% acetic acid content is the legally acceptable bottom limit (at 4 grams in 100ml), and that the diluent is water. This is the standard in place since 1977, possibly earlier - it's not a new thing, and you may typically get 4% as an ingredient in other sauces/foods, and in smaller bottles.

The expected amount in bulk gallon-plus bottles as used for canning, has always been 5%; so, people associate the bottle with the potency, and may not notice the change in labeling.

A "NOT SUITABLE FOR CANNING, PICKLING OR PRESERVATION" message needs to be on the front of the bottle for 4% vinegars.

Addendum: you should also do pH testing! The equipment is cheap, and it's an easy way to determine if you're doing the canning process right, and that the acidity is enough for preservation.

A plus, is that if you do pH testing, you may be able to boil-distill the vinegar, or modify the recipe (using less water or water-containing products) to make up for having a 4% vinegar, if you can only find that/you're stuck with gallons of the stuff.

If you've already begun canning using 4% and you haven't tested its pH at the start, do NOT keep your canned products. Consider them spoiled/miscanned, and dispose of them responsibly.


The reason 5% has been a standard in consumer-grade bulk vinegars is two-fold, from what I gather:

  • Think like a 1970s process engineer. It is easier to leave a "fudge factor" of one percent, and process/distill/dilute to a target of 5%, in large amounts. If it lands on 6 or 4 percent, as a food products company, you'll be hit for a mismeasurement, a quality foul; but not an adulteration, which is a disqualifying fuckup.
  • There's been no need to reduce the acid concentration to 4% outright, because vinegar is relatively cheap to process. Hell, the purified water may be more of the cost than the acid fraction itself, in a large bulk jug.

Nowadays, more precise tooling, process stills and measurements are available, and it winds up being a small fraction cheaper to dilute the acid/vinegar product further... so they do, now.


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in reply to @stu's post:

this might be a stupid question but: if the vinegar is lower acidity in the same volume because it's been slack filled with water, could you boil it to remove some water and make it a safe % acid again, or would boiling it ruin the vinegar for other reasons?

this is not a defense of the food companies because increasing amounts of slack fill in various packaged foods has been a thing for awhile now and it sucks eggs, i'm just wondering if there's a way to salvage the unusable vinegar or if you just have to suck it up and buy better vinegar

In theory yes, but since the boiling point of Acetic acid(the acid in vinegar) is quite close to that of water(118 to 119 °C; 244 to 246 °F), it becomes a race of reducing the water before you reduce the acid.

I've done this, and checked with pH indicator strips to make sure.

The water boiling keeps the temperature of the water at the boiling point, until it is all boiled away (at standard temperatures, pressures/depths, etc.)

You may lose some vinegar product through the boiling process (it can be carried off with steam, or vaporize through a churning boil, and something to do with Raoult's Law), but because the water boils first, the vinegar will concentrate, even if you lose some.

It's actually much easier to concentrate vinegar by freeze distilling it than by boiling it. If you cool acetic acid, at about 2°C a solid mixture of water and acetic acid that's a higher concentration than the original solution will start freezing and you can pull that out. You can test that stuff's concentration by testing the PH and mix it with some of your original vinegar till you get it up to whatever concentration you need (unless you just want the concentrated acetic acid). Be careful handling the concentrated stuff, it's not hyper dangerous but it's definitely a lot more caustic than regular vinegar if it's fairly concentrated (which is why they sell it diluted).

Freezing is definitely a better way to concentrate it over a great amount - say, to get 30-45% acid for cleaning.

For food reasons, to bring it from 4 to 5 or 6 percent, boiling might be slower, but it is easier to control and less likely to overshoot by much.

You can't overshoot by much using the freezing method if you pull the ice off of say 500ml of vinegar and put it in another 500ml of vinegar. Whatever method is most convenient for a given person is probably the best method to use though. I'm not sure boiling even is slower. Boiling is certainly less energy efficient, but that's not really a huge deal for home purposes unless you want to make quite a lot.

The main safety concern I'd have with boiling is sometimes you can get reactions with something you're distilling at boiling temperature and your pot or other equipment and end up with some substances you'd rather not have in your output. I know alcohol stills run into this with metal alloys sometimes. I doubt you'd use anything with lead or arsenic which are issues with stills. But I wouldn't be at all surprised if you can inadvertently introduce some metal acetates into your vinegar from the pot. At higher temperatures I think even dilute acetic acid can corrode copper alloys, steel, and at least some aluminum and stainless steel alloys (including ones used in cookware). So that's most pots. If you're going to boil vinegar it might be best to do it in a borosilicate glass container or an inert ceramic unless you can find confirmation a metal container is made of something that's safe with hot acetic acid.

The thing is though, all canning recipes I've seen that call for a vinegar brine further dilute with more water, and so most if not all could be adjusted to achieve an identical final brine using 4% vinegar just by varying the relative proportions of those two ingredients.

This is by no means a defense in the "now less for the same price!" of it, but if that's becoming more standard on the shelves canning authorities could (and imo should) start providing adjustment notes along the lines of "if using 4% vinegar instead use this much vinegar and this much water," the same way they provide adjustments for processing time at altitude, so home canners can safely preserve with whatever vinegar is available to them (the maths aren't terribly complicated but can totally understand not recommending home canners diy there since that's potentially a pretty high stakes calculation mistake)

i think the bigger risk is just putting it on the shelves where the 5% was in nearly the same packaging and the buyer not noticing they got something different

Agreed! But now that it's on the shelves it might behoove providers of safe canning recipes to adapt. The added note might even be more indication than just the little "(5%)" in the ingredients list for users to check their labels.